Art. 3. Hospital ships, equipped wholly or in part at the expense of private individuals or officially recognized societies of neutral countries shall be respected and exempt from capture, on condition that they are placed under the control of one of the belligerents, with the previous consent of their own Government and with the authorization of the belligerent himself, and that the latter has notified their names to his adversary at the commencement of or during hostilities, and in any case, before they are employed.